Most of the energy used in the world is derived from the combustion of carbon and hydrogen-containing fuels such as coal, oil and natural gas. In addition to carbon and hydrogen, these fuels contain oxygen, moisture and contaminants such as ash, sulfur (often in the form of sulfur oxides, referred to as “SOx”), nitrogen compounds (often in the form of nitrogen oxides, referred to as “NOx”), chlorine, mercury, and other trace elements. Awareness regarding the damaging effects of the contaminants released during combustion triggers the enforcement of ever more stringent limits on emissions from power plants, refineries and other industrial processes. There is an increased pressure on operators of such plants to achieve near zero emission of contaminants.
Numerous processes and systems have been developed in response to the desire to achieve near zero emission of contaminants. Systems and processes include, but are not limited to desulfurization systems (known as wet flue gas desulfurization “WFGD” and dry flue gas desulfurization “DFGD”), particulate filters (including, for example, bag houses, particulate collectors, and the like), as well as the use of one or more sorbents that absorb contaminants from the flue gas. Examples of sorbents include, but are not limited to, activated carbon, ammonia, limestone, and the like.
It has been shown that ammonia efficiently removes CO2, as well as other contaminants, such as sulfur dioxide (SO2) and hydrogen chloride (HCl), from a flue gas stream. In one particular application, absorption and removal of CO2 from a flue gas stream with ammonia is conducted at a low temperature, for example, between 0 and 20 degrees Celsius (0°-20° C.). To safeguard the efficiency of the system, and to comply with emission standards, maintenance of the ammonia within the flue gas stream treatment system is desired.